1. Field of the Invention
The present invention relates to a technology for removing, by polishing, an unnecessary part of a metallic film from the periphery of a device wafer which is provided with the metallic film on a surface thereof.
2. Description of the Related Art
In FIG. 10, a semiconductor wafer 1, which is a so-called device wafer, is shown. The wafer 1 is disc-shaped and includes inclined faces 2a and 2b, which are formed by chamfering the wafer 1 at both sides of the periphery thereof, and a peripheral face 3 disposed between the inclined faces 2a and 2b. The wafer 1 is provided with a metallic film 4 deposited on the wafer 1 from the inclined face 2a disposed at a front face of the wafer 1 to the peripheral face 3 and the inclined face 2b which is disposed at a rear face of the wafer 1.
In the device wafer 1, a part n of the metallic film 4 disposed at the periphery of the wafer is not necessary. The part n is likely to be removed by being brought into contact with a chuck during the transportation of the wafer, which causes dust or produces a defective product; therefore, various methods have been used for removing the part n. In this case, it is important to form a perpendicular end 4a of the remaining metallic film 4, as shown in FIG. 11. When the end 4a is inclined, as shown by a dotted line, the metallic film 4 is easily removed at this part.
A method for removing the unnecessary part of a metallic film is disclosed in, for example, Japanese Patent No. 3111928, in which a wafer rotating about an axis thereof is pressed onto a polishing pad at the periphery of the wafer, whereby a part of a metallic film disposed at the periphery and toward the rear face of the wafer is removed by varying the angle of the polishing pad. However, the end of the metallic film becomes inclined with the metallic film being cut in an oblique direction by the polishing pad and cannot be formed perpendicularly. Since the angle of the polishing pad must be varied in order to polish the overall surface of the periphery of the wafer, there is a drawback in that a driving mechanism having a complex structure is required and polishing is performed inefficiently over a long time.
Other methods for removing the unnecessary part of the metallic film disposed at the periphery of a wafer are disclosed in, for example, Japanese Unexamined Patent Application Publication No. 9-186234, one of which involves the wafer being polished such that a belt-shaped polishing cloth wraps around the wafer which rotates about an axis thereof and is pressed onto the wafer at the periphery thereof. In another method, the wafer is polished in such a manner that the polishing pad is fixed to a disc-shaped stage which rotates about an axis thereof and the periphery of the rotating wafer is pressed onto the polishing pad at a right angle such that a part of the wafer is pushed into the polishing pad.
However, in these methods, the belt-shaped polishing pad or the disc-shaped polishing pad comes into contact with the surface of the wafer in an oblique direction. Therefore, the end of the metallic film is cut in the oblique direction and cannot be formed perpendicularly.
For example, in Japanese Unexamined Patent Application Publication No. 2000-68273, a method for removing the metallic film disposed at the periphery of a front face of a wafer is disclosed, in which the wafer is polished by a rotating drum-shaped polishing head being pressed onto the periphery of the front face of the wafer which rotates about an axis thereof. However, the metallic film 4 of the wafer 1 shown in FIG. 10 disposed on the inclined faces 2a and 2b and the peripheral face 3 cannot be removed by this method except for the metallic film disposed at the periphery of the front face of the wafer. As a result, efficiency of the operation is deteriorated and scars due to a chuck are likely to occur because the wafer must be repeatedly chucked by the chuck.
Accordingly, it is an object of the present invention to provide a technology for removing an unnecessary part of a metallic film from the periphery of a device wafer, so as to efficiently form a perpendicular end of the metallic film by once chucking the device wafer using polishing members for polishing the device wafer at inclined faces formed with both sides of the periphery of the device wafer being chamfered, a peripheral face disposed between the inclined faces, and the peripheral edge of a front face of the device wafer in one process stage.
To this end, according to the present invention, a polishing apparatus for polishing a periphery of a device wafer is provided, which comprises a chuck table which chucks the device wafer provided with a metallic film deposited on inclined faces formed by chamfering both sides of the device wafer at the periphery thereof, a peripheral face disposed between the inclined faces, and a front face of the device wafer, and which rotates the device wafer about the axis thereof at a predetermined speed; a first inclined-face-polishing member and a second inclined-face-polishing member each having an arc-shaped work face and an axis which is inclined with respect to an axis of the device wafer, the work face of the first inclined-face-polishing member being positioned so as to come into line-contact with the inclined face disposed at the front face of the device wafer and the work face of the second inclined-face-polishing member being positioned so as to come into line-contact with the inclined face disposed at a rear face of the device wafer; a peripheral-face-polishing member having an arc-shaped work face and an axis which is parallel to the axis of the device wafer, the work face being positioned so as to come into line-contact with the peripheral face of the device wafer; and a peripheral-edge-polishing member formed as a disc rotatable about an axis thereof either perpendicular or parallel to the axis of the device wafer, a work face of the peripheral-edge-polishing member being positioned so as to come into planar contact with the front face of the device wafer at a peripheral edge thereof.
In the polishing apparatus according to the present invention, as described above, the inclined faces, the peripheral face, and the peripheral edge disposed at the periphery of the wafer held by a chuck are polished by the inclined-face-polishing members, the peripheral-face-polishing member, and the peripheral-edge-polishing member, respectively, whereby the wafer can be polished at the overall surface of the periphery thereof by once chucking the wafer, thereby suppressing damages due to chucking to a lowest level. Since the inclined-face-polishing members and the peripheral-face-polishing member are individually provided with arc-shaped work faces which come into line-contact with the inclined faces and the peripheral face, respectively, for polishing, the polishing can be performed efficiently in a short time. Since the peripheral-edge-polishing member comes into planar contact with the front face of the wafer at the peripheral edge thereof, the metallic film can be removed so that the end thereof is formed perpendicularly.
According to an embodiment of the present invention, the polishing apparatus may further comprise at least one feed mechanism for moving the inclined-face-polishing members and the peripheral-face-polishing member, each in a direction parallel to the axis thereof; at least one linear guide mechanism for supporting the inclined-face-polishing members and the peripheral-face-polishing member, each being movable in a direction perpendicular to the axis thereof; and at least one load-applying mechanism for bringing the inclined-face-polishing members and the peripheral-face-polishing member into contact with the wafer, each at a predetermined pressure.
The polishing apparatus may further comprise a first guide mechanism for supporting the peripheral-edge-polishing member movable in directions toward and away from the device wafer; a load-applying mechanism for bringing the peripheral-edge-polishing member into contact with the front face of the device wafer at a predetermined pressure; and a second guide mechanism for moving the peripheral-edge-polishing member in a radial direction of the device wafer so that the width of the metallic film to be removed is controlled, and a driving source.
According to another embodiment of the present invention, the first inclined-face-polishing member and the second inclined-face-polishing member may be disposed so as to oppose each other and the peripheral-face-polishing member, and the peripheral-edge-polishing member may be disposed so as to oppose each other in a direction differing by ninety degrees from the direction in which the first inclined-face-polishing member and the second inclined-face-polishing member oppose each other.
According to the embodiment of the present invention, the second guide mechanism for the peripheral-edge-polishing member may comprise a supporting table which is movable along an apparatus body in the radial direction of the device wafer and a driving source for driving the supporting table, the first guide mechanism may be formed such that the supporting table supports a supporting frame which holds the peripheral-edge-polishing member so that the supporting frame is movable in the directions toward and away from the device wafer, and the load-applying mechanism may be connected to the supporting frame and may function to reduce a sum of the load of the supporting frame and components mounted thereon, thereby applying the reduced load as a work load to the device wafer.
According to the present invention, the work face of the peripheral-edge-polishing member may be provided at the periphery of the peripheral-edge-polishing member and be formed as a short cylinder which has a uniform diameter and a length in the axial direction greater than the width of the metallic film to be removed, the work face being rotatable about the axis perpendicular to the axis of the device wafer.
The work face of the peripheral-edge-polishing member may be flat, be provided on a surface of at least the peripheral edge of the peripheral-edge-polishing member, may have a width in the radial direction greater than the width of the metallic film to be removed, and may be rotatable about the axis parallel to the axis of the device wafer.
According to the present invention, a method for polishing a periphery of a device wafer comprises the steps of chucking and rotating the device wafer about an axis thereof at a predetermined speed, the device wafer being provided with a metallic film deposited on inclined faces formed with by chamfering both sides of the device wafer at the periphery thereof, a peripheral face disposed between the inclined faces, and a front face of the device wafer; bringing an arc-shaped work face of a first inclined-face-polishing member into line-contact with the inclined face disposed at the front face of the device wafer and the arc-shaped work face of a second inclined-face-polishing member into line-contact with the inclined face disposed at a rear face of the device wafer, the first and second inclined-face-polishing members being each inclined with respect to the axis of the device wafer; bringing the arc-shaped work face of a peripheral-face-polishing member into line-contact with the peripheral face of the device wafer, the peripheral-face-polishing member being parallel to the axis of the device wafer; and bringing a disc-shaped work face of a peripheral-edge-polishing member into planar contact with the front face of the device wafer at a peripheral edge thereof, the peripheral-edge-polishing member rotating about an axis thereof either perpendicular or parallel to the axis of the device wafer. The inclined faces, the peripheral face, and the peripheral edge of the device wafer are polished simultaneously by the respective polishing members, whereby an unnecessary part of the metallic film is removed from the vicinity of the periphery of the device wafer.